This invention relates in general to an image forming apparatus and more particularly, to pin corona devices that are used for media sheet detacking in electrostatographic imaging systems.
An electrostatographic copying process includes exposing a substantially uniform charged photoreceptive member to a light image of an original document. This exposure selectively discharges areas of the charged photoreceptive member that correspond to non-image areas in the original document, while maintaining the charge in the areas corresponding to image content. Selectively discharging areas on the photoreceptive member generates an electrostatic latent image of the original document on the photoreceptive member. The electrostatic latent image is subsequently developed into a visible image by a process in which a charged developing material is deposited onto the photoconductive surface of the photoreceptor. The developing material is attracted to the charged image areas of the photoreceptive member and then the developing material conforming to the latent image is then transferred from the photoreceptive member to a media sheet. The media sheet is transported to a fusing station where the image may be permanently affixed to provide a reproduction of the original document. In a final step, the photoconductive surface of the photoreceptive member is cleaned to remove any residual developing material in preparation for another imaging cycle.
The electrostatographic process is useful for light lens copying from original images, as well as, for printing documents from electronically generated or stored original images. Analogous processes also exist in other electrostatographic applications, such as, for example, iconography where charge is selectively deposited on a charge retentive surface in accordance with an image stored in electronic form.
Electrostatographic imaging machines often use corona devices for charging a surface with electrostatic fields generated by the corona devices. Such corona devices are primarily used to deposit charge on the photoreceptive member prior to exposure to the light image described above. Corona devices may also be used in the transfer of an electrostatic image from a photoreceptor to a transfer substrate, in the tacking and detacking of paper sheets to or from the imaging member by applying a neutralizing charge to the paper, and, in the conditioning of the imaging surface prior to, during, and after deposition of toner on the imaging surface to improve the quality of the xerographic output copy.
A corona generating device, or corotron, typically includes a pin array having a plurality of electrostatic field emitters that terminate in pointed ends. A corotron is coupled to a source of high voltage so electrostatic fields are generated at the pointed tips in the pin array. If the corotron is in the vicinity of the media path in an electrostatographic imaging machine, a potential hazard is presented to an operator or technician when a media sheet jams the media path in the area of the corotrons. This hazard arises from the requirement to reach into the machine past one or more corotrons to remove the jammed sheet or sheets. For example, to clear a paper jam in some current machines, the transfer deck needs to be pivoted away from the photoreceptor to release the sheets for removal from the media path. Reaching into this area, however, may result in injury if the operator or technician contacts the pointed ends of a pin array. This injury risk is addressed by the safety guard structure disclosed in the co-pending patent application entitled “Corotron Pin Guard” having Ser. No. 11/265,478 that was filed on Nov. 2, 2005, which is assigned to the assignee of this application.
Another way to reduce the risk of injury is to reduce the likelihood of a paper jam caused in the vicinity of the corotrons so that an operator need not remove a paper jam. One cause of paper jams in the vicinity of a detack corotron arises from curled paper edges getting caught in the detack corotron. A leading or trailing edge of a paper sheet may curl away from the photoreceptor and get caught in the detack corotron as the detack corotron applies charge to the back of the paper sheet to help release the sheet from the photoreceptor. Additional causes for curled paper edges include environmental factors in the media sheet path such as heat and other conditions occurring in the machine.